The present invention relates to a composite material for balloon and a balloon made thereof. More particularly it relates to a transparent composite material for balloon having an excellent gas barrier to helium gas, hydrogen gas or the like and a balloon made thereof.
Heretofore balloons with a variety of sizes are employed for use in toys, advertising media, articles for display, and the like. Most balloons are used in a state of floating in the air with being filled with helium gas or hydrogen gas.
In order to endow a balloon with a sufficient buoyancy in the air, it is necessary to make the specific gravity, on the basis of air, of the balloon filled with a gas not more than 1. In order to achieve this, it is necessary to select, as a gas to be filled, as light a gas as possible, and as a balloon material, a material which is light and has the property that the gas filled in the balloon does not leak out through the wall of the balloon and such a great tensile strength that the balloon does not easily burst.
Rubber materials are used as the material for small-sized balloons such as toy balloons. However, common balloon materials are plastic materials having a gas barrier to helium gas or hydrogen gas, laminated with a sealant film such as polyethylene film or nonstretched polypropylene. Examples of the gas barrier plastic materials are plastic films of ethylene-vinyl alcohol copolymer, nylons, polyethylene terephthalate (PET), and vinylidene chloride resin-coated nylon films or PET films. Other laminated materials are also used wherein a nylon film or a PET film which is laminated with an aluminum leaf or has a deposition layer of aluminum or other metals to improve the gas barrier is laminated with a sealant film such as polyethylene film or nonstretched polypropylene film.
However, the above-mentioned rubber material has the drawbacks as follows: It has a poor gas barrier and a balloon made thereof is very easily broken. Further the inside of the balloon is not easily visible because of its poor transparency.
On the other hand, balloons made of the above-mentioned plastic materials are hard to be broken because of their great tensile strength. However, there is a problem that because the plastic materials do not have a sufficient gas barrier, the gas contained in the balloon escapes through its wall for a comparatively short time so that the balloon loses buoyancy. When it is tried to improve the gas barrier by using a thicker plastic film, there are problems such as the decrease in buoyancy due to the increase in weight and the losing of flexibility.
The plastic materials laminated with an aluminum leaf and the plastic materials provided with a metal deposition layer thereon are desirable because of their good gas barrier. However, the use thereof are limited because the inside of the balloon is invisible.
It is an object of the present invention to provide a composite material for balloon which is transparent and has an excellent gas barrier to helium gas or hydrogen gas.
Another object of the present invention is to provide a balloon the inside of which is visible and which retains the buoyancy for a long period of time.
These and other objects of the present invention will become apparent from the description hereinafter.